1. Field of the Invention
The present invention relates to a synthetic vascular prosthesis used to replace or bypass a lesioned portion of an in vivo blood vessel affected by an obstructive or distentive lesion.
2. Prior Art
When an obstructive or distentive lesion is produced in an in vivo blood vessel, surgery may be carried out to bypass or to replace the in vivo blood vessel using a substitute blood vessel. The substitute blood vessel may be either a blood vessel section obtained from a human body or a synthetic vascular prosthesis formed of materials such as polytetrafluoroethylene.
There are two methods for connecting the synthetic vascular prosthesis to the in vivo blood vessel. FIG. 5A shows an end-to-end anastomosis for an end 1a of the in vivo blood vessel 1 and an end 2a of the synthetic vascular prosthesis 2. FIG. 5B shows an end-to-side anastomosis for an outer surface 1b of the in vivo blood vessel 1 and the end 2a of the synthetic vascular prosthesis 2.
In the case of using the end-to-side anastomosis, first, a slit-shaped opening 3 is formed on the outer surface 1b of the in vivo blood vessel 1, as shown in FIG. 6. The end 2a of the synthetic vascular prosthesis 2 is deformed, so as to conform to the slit-shaped opening 3. Then, a circumference of the end 2a is sutured to a circumference of the opening 3. In this suturing procedure, as shown in FIG. 7, both the circumference of the end 2a and the circumference of the opening 3 are normally bent outwardly, so that an inner face of the end 2a and an inner face of the opening 3 are brought into contact with each other. Then, the contact portion is sutured using a suturing thread 4 to complete the end-to-side anastomosis procedure. This inside-to-inside suturing is desirable because the outside of the blood vessel has a property of coagulating blood.
Various lesions in blood vessels may be produced if blood flow in the blood vessels is too rapid or too slow, if break away is generated in the blood flow, or if shearing stress in the blood flow is too large or too small.
Conventional end-to-side anastomosis has a problem in that a cross section of the blood flow path alters abruptly in the region, where the end 2a of the synthetic vascular prosthesis 2 is deformed into a slit-shape, and where the blood flows from the synthetic vascular prosthesis 2 into the in vivo blood vessel 1, so that the blood flow rate and the shearing stress change significantly.
In the case of using the end-to-side anastomosis, the synthetic vascular prosthesis should also be provided with a predetermined cross sectional area, even if it is deformed into a slit-shape. Consequently, this anastomosis method has a problem in that the length of the suturing is increased, because the more the end 2a is deformed, the greater the circumference of the end 2a, for the same predetermined cross sectional area.
Moreover, it is complicated to form a slit-shaped opening on the outer surface of the blood vessel and to bend the circumference of the opening outwardly, so that the procedure has a further problem in that it requires considerable time to complete it.
Furthermore, as the end 2a of the synthetic vascular prosthesis 2 is deformed to be sutured with the in vivo blood vessel 1, additional shearing stress is applied around the connected region of the blood vessel 1, so that the cross sectional shape of the blood vessel 1 may be altered. Thus, a further problem exists in that lesions may be produced in the in vivo blood vessel 1 around the connected region due to the additional shearing stress or the alteration of the cross section.